This isn't really the same thing as Refined Github though. It's just redirecting to the new Mobile Twitter. I've yet to notice a missing feature (although there are things missing that I don't consider "features", like trending topics and moments). It also works far more reliably for me: for example, try scrolling several dozen tweets down the feed in both Mobile and Desktop Twitter, clicking on a tweet, then clicking back. I've yet to see Mobile lose my place, whereas Desktop does more often than not, and when it doesn't it has to spend a minute triggering its own infinite scroll.
Similar branding suggests similar functionality, i.e. not overhauling, but "refining," i.e. making useful small improvements. Yes, there are missing features - from account management ones to little things like being able to mention somebody while on their profile.